Pneumatic tires for motor vehicles are built the green or uncured state and are subsequently cured or vulcanized by application of heat and pressure in a mold. The mold is contained in a press, which permits the application of pressure. The green or uncured tire as built is generally toroidal in shape, symmetrical about its axis, and open at both ends. The beads are at the two ends of the green tire, the tread is in the middle, and the sidewalls lie between the tread and the respective beads, in both radial and bias ply tires.
After a green tire has been built, it is transported to the site at which the mold is located. The green tire is placed in a green tire holder where it stays until a mold becomes available. When a mold is available, an automatic loader picks up the green tire from the holder and places it in a mold.
Sometimes a green tire is stored for a while before curing, since the time between building a tire and curing is somewhat variable. Usually no particular attention is paid to the manner in which the tire is stored. The tire may simply lie on its side, for example. Since the tire is uncured, some plastic flow may take place, resulting in distortions in shape. Usually the tire is not symmetical, i.e. it is "out-of-round", after such plastic flow has taken place. If a tire of such shape is loaded into a mold and cured, it will be cured unevenly, resulting in a poor quality tire.
Various types of holders for green tires are known. Some holders have a bead centering device and support means capable of supporting the outside surface of a tire at either the sidewall or the edge of the tread. Such green tire holders are generally intended for use on one tire size only because the distance between the bead centering device and the support means is not adjustable. Since there are a number of models of automobiles with varying tire sizes on the road, a tire holder intended for only one size of tire does not properly support tires of other sizes, even when the other size differs only slightly from the size for which the holder is built. This too results in improper support for the green tire. Such a tire holder does not allow a green tire to recover from distortion in shape; in fact, it may permit further distortion with the attendant poor quality in the tire.